Optical disk substrate and molding material therefor

ABSTRACT

An optical disk substrate formed of an aromatic polycarbonate resin obtained by a reaction between an aromatic dihydroxy compound and a carbonate diester and in which the content of undissolved substances that emit light by irradiation with light having a wavelength of 380 nm and have a size of 30 μm or greater is 100 pieces or less per kg of said resin, and a molding material therefor. 
     According to the present invention, there can be provided an optical disk substrate in which the number of white spots that occur in the passage of a long period of time is very small and the reliability of writing and reading of information is highly stable.

DETAILED DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disk substrate and a moldingmaterial therefor. More specifically, it relates to an optical disksubstrate that is formed of an aromatic polycarbonate resin and canmaintain high reliability for a long period of time, and a moldingmaterial therefor.

2. Prior Art

For a transparent substrate of an optical information recording mediumthat is a recording medium for recording and/or reproducing informationwith a laser beam, such as an audio disk, a laser disk, an optical diskmemory, a magneto-optical disk, that is, for an optical disk substrate,generally, a polycarbonate resin is used, which is excellent over otherresins in moldability, mechanical strength, transparency, and the like.However, the polycarbonate resin having the above excellent propertieshas a defect that it is easily hydrolyzed at a high temperature under ahigh humidity to decrease its molecular weight and impact strength.Further, it has a defect that its reliability that should extend for along period of time is impaired, since a substrate made thereof iscaused to have white spots when left at high temperatures under highhumidity for a long period of time. At present, further, in substratematerials for high-density optical disks typified by DVD-ROM, DVD-Video,DVD-Audio, DVD-R and DVD-RAM as digital versatile disks (DVD), it isbeing required to satisfy higher-degree longer-term reliability.

As a method for producing a polycarbonate resin, there is known aninterfacial polycondensation method in which a dihydroxy compound andphosgene are directly reacted or a melt-polymerization method in which adihydroxy compound and carbonate diester are allowed to undergo an esterinterchange reaction under heat and under reduced pressure. Of thesemethods, the later melt-polymerization method has an advantage that apolycarbonate resin can be produced at a low cost as compared with theformer interfacial polycondensation method.

Generally, a method for producing an aromatic polycarbonate according toa conventional melt-polymerization method uses, as a catalyst component,a metal catalyst such as an alkali metal compound or an alkaline earthmetal compound. For example, JP-A-8-59975 includes a descriptionconcerning a method for producing an aromatic polycarbonate according tothe melt-polymerization method.

Disk substrates for an optical disk, a laser disk, etc., are generallyproduced by injection molding, and a molding temperature is a hightemperature of 300° C. or higher. Further, a continuous production isrequired, so that the polycarbonate resin is required to have highthermal stability. However, an aromatic polycarbonate resin obtained bya melting method in the presence of the above metal catalyst issometimes partially pyrolyzed during melt-molding due to a residualmetal catalyst, and the aromatic polycarbonate resin is poor in thermalstability. Further, a disk is caused to have white spots in itssubstrate when left at high temperatures under high humidity for a longperiod of time, and it has a defect that its reliability that shouldextend for a long period of time is impaired. In recent years, the disksubstrates are increasingly required to have further improvedperformances including a solution to the above problem.

Meanwhile, for applying an aromatic polycarbonate resin to an opticaldisk substrate, it is proposed to decrease a gelled substance content inthe resin to a specific range.

That is, it is described in JP-A-2-135222 that a gelled substance ispresent in an aromatic polycarbonate resin and that the content of thegelled substance is decreased to a specific range. In the above knowntechnique, the gelled substance present in the resin causes a refractiveindex anomaly in an optical use (particularly, a use for an opticaldisk), so that the number of gelled substances is limited to 50 piecesor less per kg of the resin. The above gelled substance refers to asubstance that remains on a filter having openings having a diameter of20 μm each when a solution of the resin in methylene chloride isfiltered. The above known technique is specifically intended forapplication to a resin obtained by a method in which an aromaticdihydroxy compound and phosgene are reacted in an organic solvent suchas methylene chloride (generally referred to as “solution polymerizationmethod”). That is, a resin according to the above solutionpolymerization method is obtained in the form of a powder, and when thepowder is pelletized by extrusion with an extruder, the resin suffers aheat hysteresis in the extruder. The above known technique is intendedfor limiting the amount of gelled substances that occur during such anoccasion to a specific range.

According to studies made by the present inventors, it has been foundthat, when a resin powder obtained by the above solution polymerizationmethod is melt-pelletized and when pellets are molded into a disksubstrate, the number of refractive index anomalies of the disksubstrate to be formed is decreased by decreasing the number of gelledsubstances in the pellets. The present inventors have made furtherstudies and have found that a disk substrate whose gelled substancecontent is decreased by the above known method shows a decrease in thenumber of refractive index anomalies immediately after its molding, butthat when it is held for a long period of time, particularly, when it isheld under high humidity at a high temperature for a long period oftime, white spots occur in the substrate and impede reading andreproducing the recorded information. While the cause therefor is notclear, it is presumably caused by inherent impurities such as a catalyst(e.g., sodium, etc.) and an organic solvent (e.g., methylene chloride)used in the solution polymerization method and oligomers.

PROBLEMS TO BE SOLVED BY THE INVENTION

Meanwhile, the present inventors have studied application of an aromaticpolycarbonate resin obtained by a reaction between an aromatic dihydroxycompound and a carbonate diester (also generally called “meltpolymerization method”) to disk substrates.

In the above melt polymerization method, a resin suffers heat hysteresisat a high temperature for a long period of time beyond comparison in theprocess of the polymerization as compared with the above solutionpolymerization. Therefore, there occur a large amount of undissolvedsubstances that are insoluble in methylene chloride solvent while theyare not removable through a filter of an extruder. The present inventorshave studied these undissolved substances and have found that thebehavior thereof differs from that of the above gelled substanceinvolved in the solution polymerization method. The types and numbers ofthe undissolved substances in a resin obtained by a melt polymerizationmethod are larger than the types and number of those in a resin obtainedby a solution polymerization method. Studies have been made with regardto influences of the types and number of the undissolved substances onrefractive index anomalies and the formation of white spots found afterholding for a long period of time.

As a result, it has been found that the number of luminous undissolvedsubstances generated by irradiation with specific wavelength (wavelengthof 380 nm), of the undissolved substances in a resin, has something todo with the number of white spots that occur after the holding for along period of time and that the number of white spots to occur can bedecreased to a tolerance limit or less by decreasing such specificundissolved substances to a specific number or less.

That is, according to the studies by the present inventors, thetolerance range of the number of the undissolved substances that emitlight by irradiation with a wavelength of 380 nm, in a resin obtained bya melt polymerization method, is 100 pieces or less per kg of the resin.While this tolerance range is broader than the tolerance range (50pieces or less) of gelled substances in the above known technique, it ispresumably because the behavior of the undissolved substances caused bythe inherent catalyst and polymerization conditions of the meltpolymerization method differs from the counterpart in the solutionpolymerization method that the number of the white spots to occur aftera disk substrate is held for a long period of time is remarkablydecreased.

The present invention has been arrived at on the basis of the revealedfact above.

MEANS TO SOLVE THE PROBLEM

The undissolved substances that emit light by irradiation with lighthaving a wavelength of 380 nm in the polycarbonate resin is assumed tobe substances that emit fluorescence due to salicylic acid esterstructure thereof. In an optical disk substrate formed of apolycarbonate resin produced by a melt-polycondensation method using acatalyst in a high-temperature reduced pressure state, the content ofthe above substances tends to increase. However, it has not been knownthat an optical disk substrate is improved in reliability for a longperiod of time by decreasing the above light-emitting substances to aspecific range or less.

According to the present invention, there is provided a molding materialfor optical use, which is an aromatic polycarbonate resin obtained by areaction between an aromatic dihydroxy compound and a carbonate diesterand in which the content of undissolved substances that emit light byirradiation with light having a wavelength of 380 nm and have a size of30 μm or greater is 100 pieces or less per kg of said resin.

According to the present invention, further, there is provided anoptical disk substrate formed of an aromatic polycarbonate resinobtained by a reaction between an aromatic dihydroxy compound and acarbonate diester and in which the content of undissolved substancesthat emit light by irradiation with light having a wavelength of 380 nmand have a size of 30 μm or greater is 100 pieces or less per kg of saidresin.

The present invention will be explained more specifically hereinafter.

The polycarbonate resin used in the present invention is a resinobtained by a melt-polymerization method based on an ester interchangeof a dihydric phenol and a carbonate precursor. Typical examples of thedihydric phenol used above include hydroquinone, resorcinol,1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene,4,4′-dihydroxydiphenyl, bis(4-hydroxyphenyl)methane,1,1-bis(4-hydroxyphenyl)-1-phenylmethane,bis{(4-hydroxy-3,5-dimethyl)phenyl}methane,1,1-bis(4-hydroxyphenyl)ethane, 1,2-bis(4-hydroxyphenyl)ethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane,bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-1-naphthylmethane, 2,2-bis(4-hydroxyphenyl)propane(so-called bisphenol A), 2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane,2,2-bis{(4-hydroxy-3-methyl)phenyl}propane,2,2-bis{(4-hydroxy-3,5-dimethyl)phenyl}propane,2,2-bis{(3,5-dibromo-4-hydroxy)phenyl}propane,2,2-bis{(3,5-dichloro-4-hydroxy)phenyl}propane,2,2-bis{(3-bromo-4-hydroxy)phenyl}propane,2,2-bis{(3-chloro-4-hydroxy)phenyl}propane, 4-bromoresorcinol,2,2-bis{(3-isopropyl-4-hydroxy)phenyl}propane,2,2-bis{(3-phenyl-4-hydroxy)phenyl}propane,2,2-bis{(3-ethyl-4-hydroxy)phenyl}propane,2,2-bis{(3-n-propyl-4-hydroxy)phenyl}propane,2,2-bis{(3-sec-butyl-4-hydroxy)phenyl}propane,2,2-bis{(3-tert-butyl-4-hydroxy)phenyl}propane,2,2-bis{(3-cyclohexyl-4-hydroxy)phenyl}propane,2,2-bis{(3-methoxy-4-hydroxy)phenyl}propane,2,2-bis(4-hydroxyphenyl)hexafluoropropane,1,1-dibromo-2,2-bis(4-hydroxyphenyl)ethylene,1,1-dichloro-2,2-bis{(3-phenoxy-4-hydroxy)phenyl}ethylene, ethyleneglycol bis(4-hydroxyphenyl)ether, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)-3-methylbutane,2,2-bis(4-hydroxyphenyl)-3,3-dimethylbutane,2,4-bis(4-hydroxyphenyl)-2-methylbutane,1,1-bis(4-hydroxyphenyl)isobutene, 2,2-bis(4-hydroxyphenyl)pentane,2,2-bis(4-hydroxyphenyl)-4-methylpentane,3,3-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-4-isopropylcyclohexane,1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,1,1-bis(4-hydroxyphenyl)cyclodecane, 9,9-bis(4-hydroxyphenyl)fluorene,9,9-bis{(4-hydroxy-3-methyl)phenyl}fluorene,α,α′-bis(4-hydroxyphenyl)-o-diisopropylbenzene,α,α′-bis(4-hydroxyphenyl)-m-diisopropylbenzene,α,α′-bis(4-hydroxyphenyl)-p-diisopropylbenzene,1,3-bis(4-hydroxyphenyl)-5,7-dimethyladamantane,4,4′-dihydroxydiphenylsulfone,bis{(3,5-dimethyl-4-hydroxy)phenyl}sulfone,4,4′-dihydroxydiphenylsulfoxide, 4,4′-dihydroxydiphenylsulfide,4,4′-dihydroxydiphenylketone, 4,4′-dihydroxydiphenyl ether and4,4′-dihydroxydiphenyl ester. These may be used alone or in combinationof two or more.

Our of these, preferred is a homopolymer or copolymer obtained from atleast one bisphenol selected from the group consisting of bisphenol A,2,2-bis{(4-hydroxy-3-methyl)phenyl}propane,2,2-bis{(3,5-dibromo-4-hydroxy)phenyl}propane, ethylene glycolbis(4-hydroxyphenyl)ether, 2,2-bis(4-hydroxyphenyl)hexafluoropropane,2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,4,4′-dihydroxydiphenylsulfone,bis{(3,5-dimethyl-4-hydroxy)phenyl}sulfone,4,4′-dihydroxydiphenylsulfoxide, 4,4′-dihydroxydiphenylsulfide, and4,4′-dihydroxydiphenyl ketone. A homopolymer of bisphenol A isparticularly preferred.

The carbonate precursor is selected from carbonate ester or haloformate.Specifically, the carbonate precursor includes diphenyl carbonate,ditolyl carbonate, bis(chlorophenyl)carbonate, m-cresyl carbonate,dinaphthyl carbonate, bis(diphenyl)carbonate, dimethyl carbonate,diethyl carbonate, dibutyl carbonate and dicyclohexyl carbonate,although the carbonate precursor shall not be limited thereto.Preferably, diphenyl carbonate or dihaloformate of a dihydric phenol isused, and more preferably, diphenyl carbonate is used. These carbonateesters may be used alone or in combination of two or more.

When the polycarbonate resin is produced by reacting the above dihydricphenol and the above carbonate precursor according to amelt-polymerization method, a catalyst, a terminal stopper and anantioxidant for the dihydric phenol may be used as required. Thepolycarbonate resin may be a polyester carbonate resin formed bycopolymerizing an aromatic or aliphatic difunctional carboxylic acid ormay be a mixture containing two or more polycarbonate resins obtained.

The reaction according to a melt-polymerization method is an esterinterchange reaction between the dihydric phenol and the carbonateester, and the reaction is carried out by a method in which in thepresence of an inert gas, the dihydric phenol and the carbonate esterare mixed under heat and a formed alcohol or phenol is distilled off.While the reaction temperature differs depending upon the boiling point,etc., of the formed alcohol or phenol, it is generally in the range offrom 120 to 350° C. In a later stage of the reaction, the formed alcoholor phenol can be easily distilled off by reducing the pressure of thereaction system to approximately 10 to 0.1 Torr (1,333 to 13.3 MPa). Thereaction time period is generally about 1 to 4 hours.

In the melt-polymerization method, further, a polymerization catalystmay be used for promoting the polymerization rate. As a polymerizationcatalyst, for example, a catalyst containing (i) an alkali metalcompound and/or (ii) a nitrogen-containing basic compound is used, andcondensation is carried out.

Examples of the alkali metal compound used as a catalyst includehydroxide, hydrogencarbonate, carbonate, acetate, nitrate, nitrite,sulfite, cyanate, thiocyanate, stearate, hydroborate, benzoate andphosphorohydride of alkali metal, and alkali metal salts of bisphenoland phenol.

Specific examples of the alkali metal compound include sodium hydroxide,potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate,potassium hydrogencarbonate, lithium hydrogencarbonate, sodiumcarbonate, potassium carbonate, lithium carbonate, sodium acetate,potassium acetate, lithium acetate, sodium nitrate, potassium nitrate,lithium nitrate, sodium nitrite, potassium nitrite, lithium nitrite,sodium sulfite, potassium sulfite, lithium sulfite, sodium cyanate,potassium cyanate, lithium cyanate, sodium thiocyanate, potassiumthiocyanate, lithium thiocyanate, sodium stearate, potassium stearate,lithium stearate, sodium boron hydroxide, lithium boronhydroxide,potassium boronhydride, sodium boron phenylate, sodium benzoate,potassium benzoate, lithium benzoate, disodium hydrogen phosphate,dipotassium hydrogen phosphate, dilithium hydrogen phosphate, disodiumsalt, dipotassium salt and dilithium salt of bisphenol A, and sodiumsalt, potassium salt and lithium salt of phenol.

The alkali metal compound as a catalyst can be used in an amount rangeof from 10⁻⁹ to 10⁻⁴ mol, preferably 10⁻⁸ to 10⁻⁵ mol, per mole of thedihydric phenol. When the amount of the alkali metal compound is outsidethe above range, undesirably, there is a problem that it causes adetrimental effect on various physical properties of a polycarbonate tobe obtained, or that the ester interchange reaction does not fullyproceed, so that a polycarbonate having a high molecular weight cannotbe obtained.

Examples of the nitrogen-containing basic compound as a catalyst includeammonium hydroxides having an alkyl, aryl or alkylaryl group such astetramethylammonium hydroxide (Me₄NOH), tetraethylammonium hydroxide(Et₄NOH), tetrabutylammonium hydroxide (Bu₄NOH), benzyltrimethylammoniumhydroxide (φ-CH₂(Me)₃NOH) and hexadecyltrimethylammonium hydroxide;tertiary amines such as triethylamine, tributylamine,dimethylbenzylamine, and hexadecyldimethylamine; and basic salts such astetramethylammonium borohydride (Me₄NBH₄), tetrabutylammoniumborohydride (Bu₄NBH₄), tetrabutylammonium tetraphenylborate (Bu₄NBPh₄)and tetramethylammonium tetraphenylborate, (Me₄NBPh₄). Of these,tetramethylammonium hydroxide (Me₄NOH), tetraethylammonium hydroxide(Et₄NOH) and tetrabutylammonium hydroxide (Bu₄NOH) are preferred, andtetramethylammonium hydroxide (Me₄NOH) is particularly preferred.

The above nitrogen-containing basic compound is preferably used in suchan amount that the amount of ammonium nitrogen atoms in thenitrogen-containing basic compound per mole of the dihydric phenol isfrom 1×10⁻⁵ to 1×10⁻³ equivalent weight. The above amount is morepreferably such that the amount based on the same standard is from2×10⁻⁵ to 7×10⁻⁴ equivalent weight, and particularly preferably suchthat the amount based on the same standard is from 5×10⁻⁵ to 5×10⁻⁴equivalent weight.

In the present invention, there may be used a catalyst generally usedfor an esterification or ester interchange reaction as required, andsuch catalyst includes alkoxides of an alkali metal or alkaline earthmetal, organic acid salts of an alkali metal or alkaline earth metal,zinc compounds, boron compounds, aluminum compounds, silicon compounds,germanium compounds, organotin compounds, lead compounds, osmiumcompounds, antimony compounds, manganese compounds, titanium compoundsand zirconium compounds. The above catalysts may be used alone or incombination of two or more. The amount of the above polymerizationcatalyst per mole of the dihydric phenol as a raw material is determinedpreferably to be 1×10⁻⁹ to 1×10⁻⁵ equivalent weight, more preferably tobe 1×10⁻⁸ to 5×10⁻⁶ equivalent weight.

In the above polymerization, further, the following compound may beadded at a later stage, or after the end of the polycondensation, fordecreasing phenolic terminal groups. Such a compound includes phenol,p-tert-butylphenol, p-tert-butylphenylphenyl carbonate,p-tert-butylphenyl carbonate, p-cumylphenol, p-cumylphenylphenylcarbonate, p-cumylphenyl carbonate, bis(chlorophenyl)carbonate,bis(bromophenyl)carbonate, bis(nitrophenyl)carbonate,bis(phenylphenyl)carbonate, chlorophenylphenyl carbonate,bromophenylphenyl carbonate, nitrophenylphenyl carbonate, diphenylcarbonate, methoxycarbonylphenylphenyl carbonate,2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman,2,4,4-trimethyl-2-(4-hydroxyphenyl)chroman andethoxycarbonylphenylphenyl carbonate. Of these, 2-chlorophenylphenylcarbonate, 2-methoxycarbonylphenylphenyl carbonate and2-ethoxycarbonylphenylphenyl carbonate are preferred, and2-methoxycarbonylphenylphenyl carbonate is particularly preferred.

In the present invention, terminals of the polycarbonate resin may beblocked with a terminal blocker. Further, desirably, the concentrationof terminal hydroxyl groups of the polycarbonate resin before additionof the terminal blocker on the basis of the total terminals is adjustedto at least 20 mol %, preferably to at least 30 mol %, still morepreferably to at least 40 mol %. In this manner, a specific terminalgroup can be introduced at a high amount ratio, and a high modificationeffect of the polycarbonate resin can be attained. Generally, concerningthe concentration of terminal hydroxy groups of the polycarbonate resinbased on the total terminals, it is advantageous to use the terminalblocker for a polycarbonate resin having hydroxyl groups whoseconcentration based on the total terminals is in the range of from 30 to95 mol %. The amount ratio of the hydroxyl group terminals of thepolycarbonate resin before addition of the terminal blocker can becontrolled on the basis of the amount ratio of the dihydric phenol andthe diphenyl carbonate that are charged as raw materials. The molaramount of the above concentration of the terminal hydroxyl groups in aconstant amount of the polycarbonate resin can be determined by aconventional method using ¹H-NMR.

When the molar amount of the total terminals of the polycarbonate resinof the present invention is 100 mol %, the molar amount of the terminalhydroxyl group of the polycarbonate resin is controlled to be preferably10 to 70 mol %, more preferably 15 to 65 mol %, still more preferably 20to 60 mol %, most preferably 20 to 45 mol %. The above mole percentageof the terminal hydroxyl groups of the aromatic polycarbonate resin canbe determined by a conventional method using ¹H-NMR.

The molecular weight, as a viscosity average molecular weight (M), ofthe polycarbonate resin is preferably 10,000 to 22,000, more preferably12,000 to 20,000, particularly preferably 13,000 to 19,000. The aromaticpolycarbonate resin having such a viscosity average molecular weight ispreferred, since it gives sufficient strength, attains excellent meltflowabillty during molding and causes no molding strain. The viscosityaverage molecular weight that is referred to in the present invention isdetermined by inserting into the following expression a specificviscosity (η_(sp)) determined using a solution prepared by dissolving0.7 g of the polycarbonate resin in 100 ml of methylene chloride at 20°C.

η_(sp)/c=[η]+0.45×[η]²c (in which [η] is an intrinsic viscosity)

[η]=1.23×10⁻⁴M^(0.83)

c=0.7

After the polycarbonate resin is produced by a melt-polymerizationmethod known per se, and in an extrusion step of obtaining apolycarbonate resin in the form of pellets to be supplied to injectionmolding (pelletization step), preferably, foreign matter is removedthrough a sintered metal filter having a filtering accuracy of 10 μmwhen the polycarbonate resin is in a molten state. It is preferred toadd additives such as phosphorus-based antioxidant, etc., as required.In any case, it is required to decrease the contents of foreign matter,impurities, a solvent, etc., in the resin as a raw material before theinjection molding so as to make them as small as possible. When anoptical disk substrate is produced from the above polycarbonate resin,an injection molding machine (including an injection compression moldingmachine) is used. While the above injection molding machine can beselected from generally used injection molding machines, it is preferredto use an injection molding machine having a cylinder and a screw madeof a material that has low adhesion to the resin and exhibitsanti-corrosion properties and anti-wearing properties, in view ofprevention of occurrence of a carbonaceious material and an improvementin reliability of the disk substrate. Concerning injection moldingconditions, preferably, the cylinder temperature is from 300 to 400° C.and the mold temperature is from 50 to 140° C., and under theseconditions, an optically excellent optical disk substrate can beobtained. In view of the object of the present invention, preferably,the molding environment is as clean as possible. It is also important toremove water by fully drying the material that is to be supplied to themolding and take care not to cause a residence that may causedecomposition of a molten resin.

The optical disk substrate of the present invention is formed of anaromatic polycarbonate resin which is obtained by a melt-polymerizationmethod and in which the content of undissolved substances that emitlight by irradiation with light having a wavelength of 380 nm and have asize of 30 μm or greater is 100 pieces or less per kg of the resin.

The undissolved substances that emit light by irradiation with lighthaving a wavelength of 380 nm will be sometimes abbreviated as“light-emitting undissolved substances” hereinafter.

While the measurement of the above light-emitting undissolved substanceswill be explained in detail later, the measurement is conducted bydissolving a polycarbonate resin in methylene chloride, filtering asolution through a filter having openings having a diameter of 30 μmeach (opening diameter), drying a residue on the filter and counting thenumber of substances that emit light by irradiation with light having awavelength of 380 nm while observing the residue through an opticalmicroscope. The number of the substances that emit light is converted toa value per kg of the resin, and the value. is taken as the content ofthe light-emitting undissolved substances.

The optical disk substrate of the present invention is formed of apolycarbonate resin having a light-emitting undissolved substancecontent of 100 pieces or less. The content of the light-emittingundissolved substances in the resin is preferably 80 pieces or less,particularly preferably 50 pieces or less.

In the present invention, it has been found that any optical disksubstrate formed of a polycarbonate resin whose light-emittingundissolved substance content is decreased to the specific range or lessas described above shows remarkably decreased occurrences of white spotsnot only immediately after molding but also after the passage of a longperiod of time. The optical disk substrate of the present invention istherefore excellent in storage of recordings and stability for a longperiod of time.

The present invention accordingly uses the resin whose light-emittingundissolved substance content is decreased to the above range, so thatthere can be provided optical disk substrates in which white spotshaving a size of 20 μm or greater each occur at an average of two orless per disk substrate (disk) having a diameter of 120 mm in anaccelerated deterioration test of holding the optical disk substratesunder conditions of a temperature of 80° C. and a relative humidity of85% for 1,000 hours. Under optimum conditions, there are providedoptical disk substrates in which the number of occurrence of the whitespots is an average of 1.5 pieces or less, and under particularlyoptimum conditions, there are provided optical disk substrates in whichthe number of occurrence of the white spots is an average of 1 piece orless.

In the present invention, the means for obtaining a polycarbonate resinhaving a light-emitting undissolved substance content satisfying theabove specific range includes the following means.

(1) Method in which a polycarbonate resin is dissolved in a good solventsuch as methylene chloride, and a solution is filtered through a filterhaving openings having a diameter of 30 μm (opening diameter) or less ata normal temperature under normal pressure, to remove solids.

(2) When a polymerization catalyst, particularly, the sodium metalcompound, is used as a catalyst in the polymerization of thepolycarbonate resin, the basic nitrogen-containing compound is used incombination so that the amount of the sodium metal compound per mole ofthe aromatic dihydroxy compound is decreased to 1×10⁻⁸ to 1×10⁻⁵ mol,preferably 1×10⁻⁸ to 5×10⁻⁶ mol, particularly preferably 1×10⁻⁸ to6×10⁻⁷ mol.

(3) In the step of producing the polycarbonate, polymerizationconditions, particularly, temperature conditions are controlled. Thatis, means are selected such that the temperature in a highesttemperature zone in the polymerization step does not exceed 340° C.Specifically, in the polymerization step, the number of rotation of astirring blade is controlled. Further, means are selected such that apolymer temperature difference between a low-temperature zone and ahigh-temperature zone during the polymerization step (in apolymerization reactor) does not exceed 50° C. Such means will beexplained further specifically later.

(4) The content of a polyfunctional compound in the dihydric phenol as araw material, particularly in bisphenol, is decreased. That is, if thedihydric phenol as a raw material contains, as impurities, trifunctionalor higher-functional compounds such as triphenol and tetraphenol, partof them cause light-emitting undissolved substances to occur.

Examples of the above triphenol includes compounds of the followingformulae (I) and (II).

(5) The carbonate diester as a raw material is selected from those whosesodium compound content is very small. The carbonate diester,particularly diphenyl carbonate, contains a very small amount of asodium compound due to a catalyst used in the step of productionthereof. Since the above sodium compound contained in a very smallamount has not a little influence on the occurrence of thelight-emitting undissolved substances in the polymerization, thediphenyl carbonate as a raw material is selected from those in which thetotal content of the sodium compound is very small.

Of the above (1) to (5), (2) to (5) are means of preventing theoccurrence of the light-emitting undissolved substances, and it isdesirable to employ a proper combination thereof. Naturally, these means(1) to (5) are mere illustrative examples, and other means may beemployed. Further, any combination of these means may be employed, orthese means may be used in combination with other means.

According to studies made by the present inventors, it has been foundthat there can be obtained a disk substrate that is further improved inthermal stability for a long period of time and exhibits a decreasednumber of white spots occurring, by decreasing the content of thelight-emitting undissolved substances in the polycarbonate resin to theabove specific range and further by (i) adjusting the relativefluorescence intensity of the resin to a specific value or less and/or(ii) adjusting the activity index of a residual catalyst of the resin toa specific value or less.

According to the present invention, further, there are provided thefollowing disk substrates (I) to (III).

(I) An optical disk substrate formed of a resin

(A) that is an aromatic polycarbonate resin obtained by a reactionbetween an aromatic dihydroxy compound and a carbonate diester,

wherein:

(B) the content of undissolved substances that emit light by irradiationwith light having a wavelength of 380 nm and have a size of 30 μm orgreater is 100 pieces or less per kg of said resin, and

(C) the resin has a relative fluorescence intensity, based on areference substance, of 4×10⁻³ or less at 465 nm when the resin ismeasured for fluorescence spectrum.

(II) An optical disk substrate formed of a resin

(A) that is an aromatic polycarbonate resin obtained by a reactionbetween an aromatic dihydroxy compound and a carbonate diester,

wherein:

(B) the content of undissolved substances that emit light by irradiationwith light having a wavelength of 380 nm and have a size of 30 μm orgreater is 100 pieces or less per kg of said resin, and

(D) the resin has a residual catalyst activity index of 2% or less.

(III) An optical disk substrate formed of a resin

(A) that is an aromatic polycarbonate resin obtained by a reactionbetween an aromatic dihydroxy compound and a carbonate diester,

wherein:

(B) the content of undissolved substances that emit light by irradiationwith light having a wavelength of 380 nm and have a size of 30 μm orgreater is 100 pieces or less per kg of said resin,

(C) the resin has a relative fluorescence intensity, based on areference substance, of 4×10⁻³ or less at 465 nm when the resin ismeasured for fluorescence spectrum, and

(D) the resin has a residual catalyst activity index of 2% or less.

In each of the above disk substrates (I) to (III) after the accelerateddeterioration test (80° C.×85%RH×1,000 hours), desirably, the number ofwhite spots having a size of 20 μm or greater per disk substrate havinga diameter of 120 mm is an average of 2 pieces or less, preferably anaverage of 1.5 pieces or less.

When the above disk substrates (I) to (III) is measured for fluorescencespectrum, the relative fluorescence intensity of the resin based on areference substance at 465 nm is 4×10⁻³ or less, preferably 3×10⁻³ orless, particularly preferably 2×10⁻³ or less. When the above relativeintensity exceeds the above value, the substrate tends to show adecrease in humidity resistance, heat resistance and mechanicalproperties.

Desirably, the following means is employed for obtaining a polycarbonateresin having a relative fluorescence intensity of the above specificvalue or less. Preferably, the amount of the polymerization catalyst isto be defined as described above, said polymerization catalyst is to bedeactivated with a sulfonic acid compound, and the amount ratio ofhydroxy groups to all the molecular terminals is to be defined withregard to terminals of molecule of the polycarbonate.

Further, preferably, the temperature of the polycarbonate resin in themelt-polymerization reaction is constantly maintained at 300° C. orlower, particularly preferably at 255° C. or lower, for obtaining apolycarbonate resin having a relative fluorescence intensity of theabove specific value or less.

Further, with regard to stirring with a polymerizer stirring blade, itis preferred to adjust a value obtained by dividing the stirring shearrate of the polymerizer stirring blade (unit: 1/sec) represented by thefollowing equation by a square of radius of the stirring blade (unit:cm) to 0.1 to 0.001 (l/(sec×cm²)), for obtaining a polycarbonate resinhaving a relative fluorescence intensity of the above specific value orless.

Stirring shear rate=peripheral velocity of stirring blades/length of gapbetween reactor and stirring blade (in which the unit of the stirringshear rate is l/sec, the unit of the peripheral velocity of the stirringblade is cm/sec, and the length of the gap of the stirring blade is cm).

With regard to the catalyst system in the production of thepolycarbonate resin, a basic nitrogen compound and an alkali metalcompound (particularly, a sodium compound) are used, and in this case,the amount of the alkali metal compound is controlled to be 5.0×10⁻⁶ molor less per mole of the dihydric phenol, whereby a polycarbonate havinga relative fluorescence intensity of a low value can be obtained. It ispreferred to employ the above means in a proper combination.

In the disk substrates (II) and (III), essentially, the resin has aresidual catalyst activity index of 2% or less, preferably 1% or less.

In the polycarbonate resin obtained by melt-polymerization, apolymerization catalyst is used for promoting the reaction thereof, andthe polymerization catalyst often remains after the polymerization. Ifthe remaining catalyst is left as it is after completion of thepolymerization, there is caused a detrimental effect that the catalyticactivity of the polymerization catalyst causes the polycarbonate resinto undergo decomposition or a re-reaction. Further, in the polycarbonateresin having such residual catalyst activity, not only the influencethereof spreads, but also there is sometimes caused a new problem on theretention of performances of the disk substrate, so that it is preferredto inhibit the residual catalyst activity.

Measurement is carried out in the following manner using a residualcatalyst activity index as an index for inhibiting the residual catalystactivity. A rotary rheometer that can measure a sample as a measurementobject for a value in a melt viscosity range is used as a measuringdevice, and a change in melt viscosity is observed while the sample isrotated in a constant direction at a constant angular velocity in anitrogen current sufficient for the freedom of the sample from oxidationwith external oxygen under constant-temperature conditions where a resinto be measured is melted. As a tool for a viscoelasticity measuringdevice for measuring the sample, a tool having the form of a conicaldisk is used such that a strain in the entire sample is constant, thatis, that the shear speed comes to be constant. That is, a change in meltviscosity per minute, calculated on the basis of the followingexpression (i), is taken as a residual catalyst activity index.$\begin{matrix}{{{Residual}\quad {catalyst}\quad {activity}\quad {index}\quad (\%)} = {\frac{\begin{matrix}{\left( {{{Melt}\quad {viscosity}\quad {after}\quad 30\quad {minutes}} -} \right.} \\{{\left. {{melt}\quad {viscosity}\quad {after}\quad 5\quad {minutes}} \right)}\quad}\end{matrix}}{{Melt}\quad {viscosity}\quad {after}\quad 5\quad {minutes} \times 25} \times 100}} & (i)\end{matrix}$

The above residual catalyst activity index is preferably 2% or less,more preferably 1% or less, still more preferably 0.5% or less, and mostpreferably 0.2% or less. When the residual catalyst activity index is inthe above range, desirably, there is almost no change in performances ofthe disk substrate with the passage of time.

For bringing the residual catalyst activity index of the resin into theabove value, effectively, not only the amount of the polymerizationcatalyst is relatively decreased, but also a deactivator for removingthe activity of the catalyst is added to the resin after completion ofthe polymerization. Examples of the above deactivator includebezenesulfonic acid, p-toluenesulfonic acid; sulfonate esters such asmethyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate,octyl benzenesulfonate, phenyl benzenesulfonate, methylp-toluenesulfonate, ethyl p-toluenesulfonate, butyl p-toluenesulfonate,octyl p-toluenesulfonate and phenyl p-toluenesulfonate: and furtherinclude compounds such as trifluoromethanesulfonic acid,naphthalenesulfonic acid, sulfonated polystyrene, a methylacrylate-sulfonated styrene copolymer, 2-phenyl-2-propyldodecylbenzenesulfonate, 2-phenyl-2-butyl dodecylbenzenesulfonate,octylsulfonic acid tetrabutylphosphonium salt, decylsulfonic acidtetrabutylphosphonium salt, benzenesulfonic acid tetrabutylphosphoniumsalt, dodecylbenzenesulfonic acid tetraethylphosphonium salt,dodecylbenzenesulfonic acid tetrabutylphosphonium salt,dodecylbenzenesulfonic acid tetrahexylphosphonium salt,dodecylbenzenesulfonic acid tetraoctylphosphonium salt, decylammoniumbutylsulfate, decylammonium decylsulfate, dodecylammonium methylsulfate,dodecylammonium ethylsulfate, dodecylmethylammonium methylsulfate,dodecyldimethylammonium tetradecylsulfate, tetradecyldimethylammoniummethylsulfate, tetramethylammonium hexylsulfate, decyltrimethylammoniumhexadecylsulfate, tetrabutylammonium dodecylbenzylsulfate,tetraethylammonium dodecylbenzylsulfate and tetramethylammoniumdodecylbenzylsulfate, although the deactivator shall not be limitedthereto. These compounds may be used in combination of two or more.

Of these deactivators, phosphonium or ammonium salt type deactivatorsare advantageous since they are stable themselves at 200° C. or higher.When the deactivator is added to the polycarbonate resin, it promptlyneutralizes the polymerization catalyst to give a stable polycarbonateresin. That is, the amount of the deactivator based on the polycarbonateresin formed after the polymerization is preferably 0.01 to 500 ppm,more preferably 0.01 to 300 ppm, particularly preferably 0.01 to 100ppm.

Concerning the amount ratio of the above deactivator to thepolymerization catalyst, further, it is preferred to use the abovedeactivator in an amount of 0.5 to 50 mol per mole of the polymerizationcatalyst. The method of adding the deactivator to the polycarbonateresin after the polymerization is not restricted. For example, thedeactivator may be added while the polycarbonate resin as a reactionproduct is in a molten state, or it may be added to the polycarbonateresin that is once pelletized and then re-melted. In the former, whilethe polycarbonate resin that is a reaction product in a molten state ina reactor or an extruder after completion of the reaction is in a moltenstate, the deactivator may be added, and the polycarbonate resin may bemolded and then pelletized through the extruder. Alternatively, thedeactivator may be added and kneaded with the polycarbonate resin at anytime when the polycarbonate resin obtained by the polymerization passesfrom the reactor to the extruder and then pelletized, whereby thepolycarbonate resin is obtained.

EXAMPLES

The present invention will be explained in detail with reference toExamples hereinafter, while the present invention shall not be limitedby these Examples. In Examples, “part” stands for “part by weight”.

In Examples, substances that occurred and white spots that occurred indisks were measured for numbers by the following methods.

(1) Measurement of Light-emitting Undissolved Substances for Numbers

A certain amount of a polycarbonate resin was dissolved in methylenechloride, a solution was filtered through a 30 μm filter at a normaltemperature under normal pressure, a residue on the filter was dried andsubstances that emit light by irradiation with light having a wavelengthof 380 nm were observed through an optical microscope to count a numberthereof. The number was converted to a value per kg of the resin, andthe value was shown.

(2) Measurement of Number of White Spots Before and AfterHigh-temperature High-humidity Treatment

For reproducing an increase in the number of white spots when a disk wasleft under severe atmosphere for a long period of time, the disk washeld in a constant-temperature constant-humidity chamber controlled tohave a temperature of 80° C. and a relative humidity of 85% for 1,000hours, and then, a number of white spots having a size of 20 μm orgreater was counted through a polarization microscope. Twenty-fiveoptical disk substrates (diameter 120 mm) were measured, and an averageof counted numbers was calculated and used as the number of the whitespots. Similar measurements were also carried out with regard to thedisk substrates before the treatment.

(3) Relative Fluorescence Intensity

A polycarbonate resin and a reference substance were measured forfluorescence intensities at 465 nm under the following conditions, and aratio thereof (relative fluorescence intensity=fluorescence intensity ofpolycarbonate resin/fluorescence intensity of reference substance) wascalculated.

Measurement conditions Apparatus Hitachi F4500 Lamp Xe, 150 W Slit widthEx/Em  2.5 mm each Photomulti plier 400 W Sample (concentration) 1 mgpolycarbonate resin 5 ml methylene chloride

Comparative Reference Substance: 1.0×10⁻³ mg/ml phenyl salicylate inmethylene chloride

(4) Residual Catalyst Activity Index

The residual catalyst activity index was measured as follows. A resinsample was dried under reduced pressure at 120° C. for 4 hours before ause for the measurement. An RDA-II model viscoelasticity measuringmachine supplied by Rheometrics Co. was used as a measuring machine, atool having the form of a conical disk having a diameter of 25 mm wasattached, and the measurement condition was set at a measurementtemperature of 270° C. under nitrogen current as proper conditions for asample under measurement. The measurement temperature was set on thebasis of measurements of temperatures in an oven. Then, a dried samplefor measurement was set and left such that the entire sample had asufficient measurement temperature, and then the sample was rotated atan angular velocity of 1 rad/second to start measurements. Thisprocedure was continued for 30 minutes, and a change in melt viscosityduring this period was observed. On the basis of the above measurements,melt viscosities 5 minutes and 30 minutes after the start of therotation were determined, and the following expression (i) was used fora calculation using these values, whereby a change in melt viscosity perminute was obtained and shown as a residual catalyst activity index.$\begin{matrix}{{{Residual}\quad {catalyst}\quad {activity}\quad {index}\quad (\%)} = {\frac{\begin{matrix}{\left( {{{Melt}\quad {viscosity}\quad {after}\quad 30\quad {minutes}} -} \right.} \\{{\left. {{melt}\quad {viscosity}\quad {after}\quad 5\quad {minutes}} \right)}\quad}\end{matrix}}{{Melt}\quad {viscosity}\quad {after}\quad 5\quad {minutes} \times 25} \times 100}} & (i)\end{matrix}$

(5) Concentration of Terminal Hydroxyl Groups

0.02 Gram of a resin sample was dissolved in 0.4 ml of chloroform andmeasured for terminal hydroxy groups and terminal phenyl groups at 20°C. by ¹H-NMR (EX-270, supplied by JEOL Ltd.), and a terminal hydroxylgroup concentration was calculated on the basis of the followingexpression (ii).

Terminal hydroxy group concentration (mol %)=(number of terminalhydroxyl groups/total number of terminals)×100  (ii)

Example 1

A polycarbonate resin was prepared as follows. A reaction vessel havinga stirrer, a rectifier column and a pressure-reducing device was chargedwith 137 parts of purified bisphenol A (BPA) and 135 parts of purifieddiphenyl carbonate (DPC) as raw materials and with 1.2×10⁻⁵ part ofsodium hydroxide and 7.3×10⁻³ part of tetramethylammonium hydroxide as apolymerization catalyst, and these were melted under a nitrogenatmosphere at 180° C.

The reaction vessel was internally pressure-reduced to 13 kPa withstirring at a rotation velocity of 40 r.p.m., and the raw materials wereallowed to react for 20 minutes while a phenol formed is distilled off.Then, the temperature in the reaction vessel was elevated to 200° C.,the pressure was gradually reduced and while phenol was distilled off,the reaction was carried out at 4.0 kPa for 20 minutes. Further, thetemperature was gradually increased and the reaction was carried out at220° C. for 20 minutes, at 240° C. for 20 minutes and at 250° C. for 20minutes. Then, while the reaction mixture was stirred at a rotationvelocity of 30 r.p.m. at 255° C., the pressure was gradually reduced,and the reaction was continued at 2.7 kPa for 10 minutes and at 1.3 kPafor 5 minutes. Then, for maintaining the temperature of a shear portionof a stirring blade and the reaction vessel where the temperature wasmost increased inside a polymerization apparatus, at 305° C. or lower,the rotation velocity was changed to 20 r.p.m. when the viscosityaverage molecular weight came to be 10,000 on the basis of arelationship between a rotation power and a viscosity average molecularweight, and finally, at 250 to 255° C./67 Pa (taking care to constantlykeep 255° C. or lower) and while the value obtained by dividing thestirring shear velocity (unit: l/sec) of the stirring blade of thepolymerization vessel with a square of the radius (unit: cm) of thestirring blade was maintained at 0.001 (l/sec×cm²), polycondensation wascontinued until the viscosity average molecular weight of the aromaticpolycarbonate resin came to be 15,300.

Then, 1.2×10⁻⁴ part of dodecylbenzenesulfonic acid tetrabutylphosphoniumsalt was added thereto, and a mixture was stirred at 260° C./67 Pa for10 minutes.

Then, the polycarbonate resin was transferred to an extruder with a gearpump. While the polycarbonate resin was somewhere in the extruder, amold release agent (0.08% by weight of glycerin monostearate) and a heatstabilizer (0.01% by weight of tris(2,4-di-tert-butylphenyl)phosphite)were added, to give a polycarbonate resin having a viscosity averagemolecular weight of 15,300, a terminal hydroxyl group concentration of37 mol %, an undissolved substance content of 7 pieces, a relativefluorescence intensity of 1.3×10⁻³ and a residual catalyst activity of0.1 (%).

A disk substrates were produced from the thus-obtained pellets by thefollowing method.

That is, the disk substrate was produced with an injection moldingmachine DISK3M3 supplied by Sumitomo Heavy Machinery Inc., and a moldhaving a cavity having a thickness of 1.2 mm and a diameter of 120 mmand having, set therein, a stamper having a concavo-convex formcorresponding to information signals, at a barrel temperature of 340° C.

An aluminum reflection layer was formed on the thus-obtained disksubstrate by sputtering, to give an optical information recordingmedium. The information recording medium was measured for an error ratiowith an evaluation apparatus CD-CATS supplied by Audio Development AB.Table 1 shows the content of substances that emitted light byirradiation with light having a wavelength of 380 nm in the substrate,as “Content of light-emitting substances”.

Example 2

Polycarbonate pellets having a viscosity average molecular weight of15,300, a terminal hydroxyl group concentration of 35 mol %, anundissolved substance content of 5 pieces, a relative fluorescenceintensity of 1.0×10⁻³ and a residual catalyst activity index of 0.1 (%)were obtained in the same manner as in Example 1 except that the sodiumhydroxide as a catalyst was replaced with bisphenol A disodium salt(approximately 5×10⁻⁷ mol/biphsenol A 1 mol). These polycarbonatepellets were evaluated in the same manner as in Example 1.

Comparative Example 1

A reactor with a thermometer, a stirrer and a reflux condenser wascharged with 219.4 parts of deionized water, 40.2 parts of a 48% sodiumoxide aqueous solution and 0.12 part of hydrosulfite, and 57.5 parts of2,2-bis(4-hydroxyphenyl)propane was dissolved with stirring. Then, 181parts of methylene chloride was added, and 28.3 parts of phosgene wasadded by blowing at 20 to 25° C. over 40 minutes, to carry out areaction, whereby a polycarbonate oligomer was obtained. The reactionmixture was temperature-adjusted to 30° C., and then, 1.24 parts ofp-tert-butylphenol and 7.2 parts of a 48% sodium hydroxide aqueoussolution were added to form an emulsion. Then, the emulsion was stirredfor 2 hours to complete the reaction.

After completion of the reaction, the emulsion was diluted by adding 246parts of methylene chloride, to form a solution of 14% by weight of apolycarbonate resin in methylene chloride. Then, an organic phase wasadjusted to be hydrochloric acid acidic and then repeatedly washed withwater. When the electric conductivity of an aqueous phase came to benearly the same as that of deionized water, a polycarbonate solution wasdropwise added to warm water in a kneader, and a polycarbonate resin wasformed into flakes while methylene chloride was distilled off. Then, theabove liquid-containing polycarbonate resin was pulverized and dried togive a polycarbonate resin powder. After the power was dried, 0.08% byweight of glycerin monostearate and 0.05% by weight of trisnonylphenylphosphite were added, and the mixture was extruded with a ventedtwin-screw extruder at a cylinder temperature of 270° C. under a ventpressure of 6.7 kPa, to form pellets. The thus-obtained pellets had aviscosity average molecular weight of 15,300, a terminal hydroxyl groupconcentration of 12 mol % and an undissolved substance content of 5pieces.

Comparative Example 2

A reactor with a stirrer and a distillation column was charged with 228parts by weight of 2,2-bis(4-hydroxyphenyl)propane and 219 parts byweight of diphenyl carbonate (supplied by Bayer AG) and with 0.0001 partby weight of sodium hydroxide and 0.0073 part by weight oftetramethylammonium hydroxide as a catalyst, and the inside of reactorwas substituted with nitrogen. The resultant mixture was heated up to200° C. to be dissolved with stirring. Then, the pressure reductiondegree was set at 4 kPa, and a major part of phenol was distilled offunder heat in 1 hour. Further, the remainder was temperature-increasedup to 290° C. and the pressure reduction degree was adjusted to 133 Pato carry out a reaction for polymerization. Then, without usingdodecylbenzenesulfonic acid tetrabutylphosphonium salt as a catalystneutralizer, the polycarbonate resin was transferred to an extruder witha gear pump. While the polycarbonate resin was somewhere in theextruder, 0.08% by weight of glycerin monostearate and 0.01% by weightof tris(2,4-di-tert-butylphenyl)phosphite were added, to give aromaticpolycarbonate resin pellets having a viscosity average molecular weightof 15,300, a terminal hydroxyl group concentration of 74 mol %, anundissolved substance content of 120 pieces, a relative fluorescenceintensity of 5.8×10⁻³ and a residual catalyst activity of 2.1.

TABLE 1 Ex.1 Ex.2 C.Ex.1 C.Ex.2 Polymerization Melting Melting SolutionMelting method method method method method Un-dissolved substances 7 5 5120 [number/kg] Residual catalyst 0.1 0.1 2.1 activity index [%]Relative fluorescence 1.3 1.0 5.8 intensity (×10³) Terminal hydroxy 3735 12 74 group (mol %) Error ratio (before 2.6 × 10⁻⁵ 2.1 × 10⁻⁵ 2.2 ×10⁻⁵ 1.2 × 10⁻³ high-temperature high- humidity treatment) AA BAA 0.10.1 0.1 1.9 AAA 0.3 0.2 2.3 3.0 Ex. = Example C.Ex. = ComparativeExample AA: Number of white spots BAA: Before high-temperaturehigh-humidity treatment AAA: After high-temperature high-humiditytreatment

What is claimed is:
 1. An optical disk substrate formed of an aromaticpolycarbonate resin obtained by a reaction between an aromatic dihydroxycompound and a carbonate diester and in which the content of undissolvedsubstances that emit light by irradiation with light having a wavelengthof 380 nm and have a size of 30 μm or greater is 100 pieces or less perkg of said resin.
 2. The optical disk substrate of claim 1, wherein,after an accelerated deterioration test (80° C.×85%RH×1,000 hours), thenumber of occurred white spots having a size of 20 μm or greater perdisk substrate having a diameter of 120 mm is an average of 2 pieces orless.
 3. The optical disk substrate of claim 1, which is formed of theresin in which the content of undissolved substances that emit light byirradiation with light having a wavelength of 380 nm and have a size of30 μm or greater is 80 pieces or less per kg of said resin.
 4. Theoptical disk substrate of claim 1, wherein the number of occurred whitespots having a size of 20 μm or greater per disk substrate having adiameter of 120 mm after the accelerated deterioration test is anaverage of 1.5 pieces or less.
 5. The optical disk substrate of claim 1,wherein said resin has a relative fluorescence intensity of 4×10⁻³ orless at 465 nm based on a reference substance when measured forfluorescence spectrum.
 6. The optical disk substrate of claim 1, whereinsaid relative fluorescence intensity of the resin is 3×10⁻³ or less. 7.The optical disk substrate of claim 1, wherein said resin has a residualcatalyst activity index of 2% or less.
 8. The optical disk substrate ofclaim 1, wherein said resin has a residual catalyst activity index of 1%or less.
 9. The optical disk substrate of claim 1, wherein the resincontains 1×10⁻⁸ to 1×10⁻⁵ mol, per mole of the aromatic dihydroxycompound, of a metal catalyst and 0.5 to 50 mol, per mole of the metalcatalyst, of a catalyst deactivator.
 10. The optical disk substrate ofclaim 1, wherein said resin has a viscosity average molecular weight of10,000 to 22,000.
 11. The optical disk substrate of claim 1, whereinsaid resin is an aromatic polycarbonate resin obtained by usingbisphenol A as the aromatic dihydroxy compound.
 12. An optical disksubstrate formed of a resin, wherein; (A) the resin is an aromaticpolycarbonate resin obtained by a reaction between an aromatic dihydroxycompound and a carbonate diester, (B) the resin has 100 pieces or lessper kg of said resin of undissolved substances that emit light byirradiation with light having a wavelength of 380 nm and have size of 30μm or greater, (C) the resin has a relative fluorescence intensity,based on a reference substance, of 4×10⁻³ or less at 465 nm when theresin is measured for fluorescence spectrum, and (D) the resin has aresidual catalyst activity index of 2% or less.
 13. The optical disksubstrate of claim 12, wherein after an accelerated deterioration test(80° C.×85%RH×1,000 hours), the number of occurred white spots having asize of 20 μm or greater per disk substrate having a diameter of 120 mmis an average of 2 pieces or less.
 14. A molding material for opticaluse, which is an aromatic polycarbonate resin obtained by a reactionbetween an aromatic dihydroxy compound and a carbonate diester, andwhich is also a resin in which the content of undissolved substancesthat emit light by irradiation with light having a wavelength of 380 nmand have a size of 30 μm or greater is 100 pieces or less per kg of saidresin.
 15. The molding material for optical use as recited in claim 14,wherein said resin has a relative fluorescence intensity, based on areference substance, of 4×10⁻³ or less at 465 nm when the resin ismeasured for fluorescence spectrum.
 16. The molding material for opticaluse as recited in claim 14, wherein said resin has a residual catalystactivity index of 1% or less.
 17. An optical disk formed from a moldingmaterial comprising an aromatic polycarbonate resin obtained by areaction between an aromatic dihydroxy compound and a carbonate diester,wherein the resin has a content of undissolved substances that emitlight by irradiation with light having a wavelength of 380 nm and have asize of 30 μm or greater which is 100 pieces or less per kg of saidresin.
 18. The optical disk as recited in claim 17, wherein said resinhas a relative fluorescence intensity, based on a reference substance,of 4×10⁻³ or less at 465 nm when the resin is measured for fluorescencespectrum.
 19. The optical disk as recited in claim 17, wherein saidresin has a residual catalyst activity index of 1% or less.